Abstract

Monolithic passively mode-locked (PML) semiconductor lasers are attractive high-speed photonic emitters potentially enabling novel future secure communication schemes [1]. In this contribution, mutual all-optical injection of two PML InAs/InGaAs quantum dot (QD) lasers emitting at 1250 nm with equal active region and waveguide geometry is studied experimentally for the first time and explained theoretically. The active regions of both two-section lasers consist of 5 layers of InAs/InGaAs QDs, and the emission wavelengths are at around 1255 nm. Both cavity lengths amount to 2 mm with a 0.25 mm long absorber section at the back facet that is reverse biased at 4 V. The facets are anti-reflective (front facet) and high-reflective (back facet) coated. The lasers are stabilized at different heat sink temperatures (Laser 1: 15 °C, Laser 2: 24 °C) to ensure optimum wavelength overlap. Both lasers are mutually coupled by a setup, depicted schematically in Fig. 1a). Emission beams of both lasers are individually collimated and overlapped across a distance of approximately 1.65 m. Optical fine-delay is implemented by a retro-reflector mounted on a linear translation stage.

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